Server Timing API

Hopefully you’re using the navigation and resource timing APIs to track the
performance of your site for real users. Until now, there hasn’t been an easy
way for the server to report its performance timing.

The new Server Timing API allows your
server to pass timing information to the browser; giving you a better picture
of your overall performance.

You can track as many metrics as you want: database read times, start-up time,
or whatever is important to you, by adding a Server-Timing header to your
response:

'Server-Timing': 'su=42;"Start-up",db-read=142;"Database Read"'

They’re shown in Chrome DevTools, or you can pull them out of the response
header and save them with your other performance analytics.

display: contents

The new CSS display: contents property is pretty slick!

When added to a container element, any children take its place in the DOM,
and it essentially disappears. Let’s say I’ve got two div’s, one inside the
other. My outer div has a red border, a gray background and I’ve set a width
of 200 pixels. The inner div has a blue border, and a light blue background.